I've just bought some La Sportiva Ultra Raptors, which seem in most ways like the perfect shoe for me - rugged, grippy, wide enough in the forefoot but snug in the heel with moderate 8mm drop.

I'm currently in the 'wearing on carpet at home getting comfortable with my purchase' phase and I'm worried that the extra height of padding compared to the Merrell's (while welcome for comfort) just feels like it creates more leverage for rolling an ankle.

The stack height isn't massive (22mm/29mm forefoot/heel according to Running Warehouse) - is this a legitimate concern or do I just need to adjust to the different feel?

Yes, more stack height will certainly cause more rolled ankles. But, more stack height also means a bit longer stride and a minor adjustment to gait. You need to decide which is more comfortable for you. Shoe fit is very individual specific, and much of this depends on how much weight you are carrying.

The vast majority of thru-hikers and other backpackers are using shoes with 8mm or more of stack height so you should be okay as long as your foot placement its good. I don't like really tall hiking boots for this reason but I think the stack height on your shoes will be manageable.

I do think Trail Gloves make an ankle role less likely because your entire foot can move when you hit an obstacle rather then all the movement being in your ankle. I'm not sure its just the stack height however. The entire shoe is more flexible.

If you want less stack height I really like the Altra Lone Peaks. I have two pairs I'm wearing on the carpet till I decide which size fits better but I think they will be a good compromise between the two.

22 - 29 is a fairly high stack height, and yes it could be an ankle roll concern. need to be more focused when walking/running.

I have an ankle roll problem when running generally, and have found that the narrower the heal tread the greater the tendency to roll your ankle. For me the heal tread width is a greater issue than stack height, though both are a concern.

So I tend towards shoes with wider heal tread. especially if the stack height gets up there a bit.

"For me the heal width is a greater issue than stack height, though both are a concern."

Actually that is a very good point. Another plus for the Lone Peaks would be the fairly wide heel. I feel like a high narrow heel is the worst possible combination. I did fairly well in NB 101 (10mm stack height) and one thing I liked about them was that the heel was not super narrow.

Is the Lone Peak more padded than an New Balance MT110? I am looking for something with a little more cushion that is good on scree (no eva cutouts on the sole). Otherwise I think I will be back to a 8 or 10 mm heal drop to get the extra protection.

The stack height of the Lone Peaks is 17mm. The NB110 goes from 18mm down to 14mm. So it depends on where you want more padding. If your forefoot is getting beat up the Lone Peaks might be better.

Edit - I forgot to mention, no evo cut outs which was a deal breaker for me on the minimus. And the bottom feels pretty firm. That is actually a complaint from some barefoot types that they are to stick. I'd order a pair from Runnerswarehouse.com just to try them out. Free shipping and they are on sale.